Controlling means for hoisting mechanisms



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CONTROLLING MEANS FOR HOISTING MECHANISMS Filed June 10, 1940 sSheets-Shani L0 WEE/Ni &

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July 8, 1941. E. L. SCHWARZ CONTROLLING MEANS FOR HOISTING MECHANISMSFiled June 10, 1940 3 Sheets-Sheet 2 y 1941 E. L. scHwARz 2.248 393 CONTROLLING MEANS FOR HQISTING MECHANISMS v Filed June 10, 1940 5Sheets-Sheet 5 h ereior mNG ham. i v v 30 Patented Juli 8, 1941 sMsErnst L. Schwarz, Chicago, 111., asslgnor to Whiting Corporation,Harvey, Ill., 1; corporation of Illinois Application June 10, 1940,Serial No. 339,655

Claims.

The invention relates to controlling means for hoisting mechanism.

The objects of the invention'are to provide hoisting mechanism whichcomprises an induction motor, winding mechanism operable by the motor,and an electrically-controlled brake adapted to be appliedt'o controlthe operation of the winding mechanism by'the load, with improvedcontrolling mechanism whereby: the lowering of theload may beselectively controlled by oversynchronous operation of the motor oraccurate brake-regulation according to the character of the work or foraccurate brake control in lowering varying loads; in which thecontroller is unsymmetrical to produce different regulating conditionsfor hoisting and lowering; in which the controller is provided with aplurality of sta tions for initial lowering with smooth retardation fromhigh speed to low speed; in which resistances in the motor of thelifting motor during oversynchronous lowering are so dimensioned thatthe lowering speed for the heaviest predetermined load has. a higherthan rated normal speed but limited value for safe and fast lowering forall loads; which includes a. reversing switch for selective brakeregulation or oversynchronous lowering if no brake-regulation is,desired; in which the controlling mechanism is normally set forlowering under brake-regulation and with readily operable switch-meansfor oversynchronous lowering; in which the controller is provided with aplurality of starting stations for lifting and resistance in the rotorof the lifting motor is dimensioned so that loads up to 80% of the fullload will start under brake-regulation and at the second station 100%01'the load will start slowly in hoisting so that brake-regulation will notbe necessary at the second station; in which, during initialbrake-regulated lowering, the resistance in the rotorof the liftingmotor is eliminated in lowering by the overhauling load and thebrake-regulating motor is operated responsively to the variations infrequency and voltage produced by the rotor of the lifting motor so thatit is only necessary for the regulating-hrake to dissipate the energy ofthe lowering load, thereby effecting economical use of theregulating-brake and a lower regulated speed; and other objects whichwill appear from the detailed description.

The invention consists in the several novel features which arehereinafter set forth and which are more particularly defined by claimsat the conclusion hereof.

In the drawings: Fig. l is a diagrammatic view of mechanism forcontrolling the hoisting mechanism embodying the invention. Fig. 2 is aplan of the hoisting mechanism. Fig. 3 is a side elevation of theregulating-brake and the electrohydraulic mechanism tor'controlling theapplication of the brake. Fig. 41s a section on line 4-4 of Fig. 3. Fig.5 is a diagram of a modified form of theinven'tion for-selectivelycontrolling lowering by brake-regulation or oversynchronous lowering. lr

The invention is exemplified with hoisting mechanism which comprises adrum Rfor winding and unwinding a cable for raising and lowering leads;an electric motor M for operating the hoisting mechanism and connectedto drive the drum N through suitable speed reducing gearing n ofanysuitable construction; a brake 0 adapted to be applied to the shaftoi motor M for retarding said shaft and comprising a brake-drum o andbrake-shoes o electro-divdraulic brake-controllmg device comprising a Isquirrel-cage, electric motor C and an impeller oil-pump P operable bymotor C to regulate the application of the brake-shoes to drum 0. Themotor M is of the thrce-phaseinduction asynchronous type and comprises astator M and is adapted to be connected by a three-pole line switch F toa source of high voltage current, for example 440 volts, and a rotor Mwound for low voltage, for example 140 volts.

The improved controlling mechanism-comprises a drum-type electriccontroller A ior manually controlling the operation of the hoistingmech-- anism in raising and lowering loads; a three phase transformer Gincluding a low voltage (140 volts) coil 0' connected to rotor 1% foroperating motor C responsively to variations in the voltage andfrequency produced by the rctor M of motor M, and a high voltage ciaovolts) coil 0 adapted to be connected to the stator of motor C;resistors R R R in the circuits for rotor M a relay D comprising magnetsD D for controlling switches to altemat-elzr connect the motor C to thestator M of the motor M and to the coil 9' of the transformer G; and aswitch E comprising poles e, e e for selectively con- M of motor M. Thearmatures of magnets D, D are electrically interlocked and may also bemechanically interlocked (not shown) so that when one set of switches isclosed the other will be open.

The controller A comprises a drum or and is illustrated as rotatablefrom a neutral position, indicated at zero, through seven loweringstations and seven lifting stations which are indicated by linescorrespondingly numbered.

The controller A also comprises a series of contact-fingers 23, 24, 25,25, 21 and 28 for controlling circuits through the stator M of motor Mand segmental contacts 2|, 25', 21, 28 on drum a adapted to engagefingers 24, 25, 21, 28, respectively, for raisingloads and contacts 29,24 26 2'! on the drum for engaging fingers 23, 2t, 26, 21, respectively,for lowering loads. Contacts 28, 21 21 and 26 are electricallyconnected. Contacts 21 26 are electrically connected. Contacts 23, 24'are electrically con- I press spring to release the brake-shoe fromnected. Contacts 24, 25 are electrically connected. The controller isalso provided with fingets 35, 36 and 31 engageable by segmentalcontacts 35', 36 and 31 on the drum a, respectively, in raising loadsand engageable by. segmental contacts 35", 18 and 2?", respectively, inlowering loads. The controller is also provided with contact-fingers 46,41, 48, 49, 50, SI, 52, 53 and 54 for connecting resistors R R, and Rto, and short-circuiting them from, the circuits for the rotor W of themotor M. The drum a is provided with segmental contacts 48, I1,

48, 49', 50, Si, 525,52, 54* engageable by contact-fingers 43, 41, l8,I9, 50, Si, 52, 53, 54, respectively, in raising loads and by segmentalcontacts 46 41, 48 49 50 51 52 53 54, respectively, in lowering loads.The segmental contacts on drum 0 are relatively positioned and of therelative length shown in Fig. 1. g

The controller is electrically connected to the line switch F, the rotorM, the resistors R, R, R the stator of motor C, the transformer G, therelay switches and the switch E, as illustrated in Fig. 1 and as willmore clearly appear from the description of the control mechanism. Ahigh-limit switch H is provided in the circuits between the controllerand the stator M as shown.

The impeller pump P comprises a cylinder 12 a piston p slidably mountedtherein, and a rotary impeller p adapted to force oil from the upperside of the piston to its lower side to release the brake when theimpeller is driven by motor C. The impeller is mounted in the piston andhas a sliding driving connection with the shaft of the rotor C of motorC. The stator C of motor C is mounted on the upper end of the pump. Whenthe impeller is stopped the oil flows through the openings in the pistonfrom its lower side to its upper side to apply the brake- .shoes 0 todrum 0 The piston is provided with a by-pass duct 9 so that the speed ofthe liftring of the piston will vary proportionately to the speed of theimpeller.

The brake-shoes are carried by pivoted levers 0". Piston p is connectedto shift the brakeshoes 0 by rods p, a lever o pivotally connected tothe upper end or a crosshead p on rods 11 and pivotally connected, as at0, to one of the levers o. A spring o is applied to normally force thebrake-shoes against the drum. Spring 0 surrounds a rod 0 which ispivotally connected, as at o", to one oi the brake-shoe levers andextends through a stirrup-link 0'. which is pivotally the drum. Thedegree of movement of lever 0 is responsive to the movements of piston pto graduate the force of the spring 0 and apply the brake-shoes to thedrum with varying force for regulating the braking torque.

When switch E is set in the position shown by full lines in Fig. l, theoperator, through controller A, controls the operation of brake-motor Cfor complete release of the regulation-brake and oversynchronouslowering of loads. When switch E is set into position indicated bydotted lines in Fig. l, the operation of motor C for brake-regulation iscontrolled on the first lifting station and the first lowering stationresponsively to the variation in voltage and frequency in the circuitsof rotor M.

This controlling mechanism is adapted for lifting the load withbrake-regulation at the first station for accurate placement of theloads; for

lifting the loads with-out brake-regulation; for lowering the loads withbrake-regulation at the first two lowering stations; and for loweringthe loads without brake-regulation. When switch E is set in its fullline position and the controllerdrum a is shifted to close switches :1d", d, the stator of motor C will be connected to the stator M of motorM. In lowering loads, the load overhauls the motor and drives rotor M ofmotor M. This motor then operates as an asynchronous generator anddevelops energy into the main line, and the stator of motor C has fullvoltage and completely releases the brake. When the stator of motor C isdisconnected from the stator M at switches d", d, d and magnet D closesswitches (1, d d, the stator of motor C will be connected to the rotor Mof the lifting motor through transformer G and the operation of themotor C to regulate the release of the brake will be controlled byvariation in voltage and frequency in the circuits of rotor M.

The stator windings of motor C, when switches 11'', d, d are closed, areconnected to terminals of the stator M of the hoisting motor M. Thebrake is designed to regulate slipping in response to the variations inthe pressure'of oil in the pump P which is automatically controlled bythe speed of motor C. This regulation is utilized for speed regulationin lowering and in lifting. The frequency and voltage of the currentproduced in the circuits of rotor M diminish with increasing speed andas the frequency. drops the speed of motor C drops proportionately whileit is connected to the rotor M through switches d", d, and d. Variationsin the speed of motor C produce variations in the oil pressure in theimpeller pump P and in the braking torque so that the brake can beregulated almost independently of the load. As a result, the brake iscaused to slip and eifects regulation to approximately, say, 20% of thespeeds for all loads when lifting and lowering with brake-regulation. I

' The operation will be as follows: when the drum a is in its neutralposition the drum-fingers will be disconnected from all contacts on the.

drum, the hoisting motor M will be idle, the brake-controlling motor Cwill be idle, the piston p of the impeller pump will be lowered, and

the brake-shoes will be applied to hold the drum on the shaft of thehoisting motor M and hold the load suspended therefrom. In practice, ifdesired, a. mechanical load-brake may be used to lock the drum againstlowering by the load, as well understood in the art.

Oversynchronous lowering.-The switch E is set in the position shown byfull lines in Fig. 1. When the controller drum is moved to loweringstation I, a circuit for energizing magnet D to close switches d", d, dand open switch 11 will be established as follows: pole f of switch F,conductor is, pole e of switch E, conductors g, 9 switch (1, magnet Dconductors g 9 contactor-finger 23, contacts 23, 24 finger 24, andconductor f and pole f Magnet D will close switches d (i a? and connectthe stator C of motor C to stator M of motor M through said switches andconductors 0 g and c Resistors R R R will be included through switch Ein the circuits of rotor M Rotor M at m is connected toresistor R byconductor 54 and said resistor is connected by conductor 65 to pole e ofswitch E; and said pole is connected by conductor 66 to resistor R whichis connected by conductor 69 to m of rotor M The resistor R is includedin a circuit from m on rotor M through conductor 60, resistor Rconductor 58, pole e .of switch E, conductor 55, resistor R andconductor 68 to m on rotor M The maximum resistance permitted for thispurpose is now included in the circuits for rotor M? to provide safetyfor lowering. During this lowering of the load at station I the stator Mis connected to the line. Pole of switch F is connected throughconductor 0, finger 21, contacts 21 26 finger t6 and conductor c to m. mof stator M? is connected to pole of switch F by conductor o finger 23,contacts 23 24 finger 24 and conductor f At m the stator is directlyconnected by conductor f to pole l of switch F. Fingers 23, engagecontacts 23*, 24 to establish a circuit to connect the motor C and thestator M to cause motor C to release the brake. Said circuit will be asfollows: m on stator M conductors 0', c switch d conductor 0 m on statorM conductors F, a, switch d conductor 0 m on stator M conductors c 0switch d conductor The overhauling load rotates the rotor M so the motoroperates as an asynchronous generator and develops power back into themain line. The full voltage causes the motor 0 to completely release thebrake. The ohmic value of the resistors is such that the lowering speedof the heaviest load is not too high, which would endanger the motor Mand, on the other hand,

. is sufiiciently high to allow the load to drop with sufiicient speedfor expeditiously handling the loads.

At station I, the resistors provide the highest degree of safety forlowering. As the controller is shifted to succeeding stations, anincrease of lowering speed will not occur. The load can be lowered atany desired increase of speed according to the value of the resistanceused. The degree of permissible increase depends on the winding of therotor M and its permissible overspeed.

At lowering stations 2 and 3, all of the resistors remain connected tothe rotor M as occurs at station I, and the brake remains released.

At stations I, 2 and 3, the overhauling load at tains its highestlowering speed. At lowering station 4, a portion of the resistor R isshortcircuited across conductor 55, finger 49, contact 49', contactfinger 45, conductors 62, 65 and switch E. At lowering station 5, aportion of the resistor R will be additionally short-circuited across mof rotor M, conductor 50, finger 50, contact contact 45, conductors 62,and switch E. At station 5, a portion of resistor R will be additionallyshort-circuited from m of rotor M, through conductor 54, 63 finger 5I,contact 5| across to contact 48, conductors 63, and switch E.

At lowering station I, fingers 48, 49, 50, 5|, 52, 53, 54 will engagecontacts 48 49 50, 5|", 52 53 54. All of the resistors will beshortcircuited. Resistor R will be short-circuited through conductor 84,finger 54, contacts 54', 52 contactor-finger 52 to conductors G3, 69.Resistor R will be short-circuited through conductor 50, finger 53,contacts 53 52 finger 52 and conductors 53, 59. Resistor R will beshortcircuited through conductors 59, 63, finger 52, contacts 52 53finger 53 and conductor 50. At station I, thespeed is some per cent.above synchronous,

Lowering with brake-regulation.-Switch E will be set in the positionindicated by dotted lines in Fig. 1. In regulated-brake lowering,station I is used for the lowest lowering speed and station 2 for aslightly higher lowering speed.

At lowering station I, fingers 35 and 31 will engage contacts 35 and31', respectively, for energizing magnet D through a circuit whichincludes: conductor 1 pole e of switch E, conductor g finger 31, contact31* across contact 36 to contact 35", finger 35, conductor, a, switch dmagnet D conductors g g finger 23, contacts 23*, 24 finger 24, conductorf and pole f Switch a. will then be opened andswitches d, d and d willbe closed to connect the stator of motor C to the rotor M through thetransformer G.

Theoretically, the rotor voltage and frequency are zero when the motorruns synchronously and when the lifting motor is stalled the rotor hasfull voltage and frequency. Resultantly, the speed of the motor C isproportional to the speed and consequent variations in frequency in theI, without resistance in the .rotor circuit and withoutmotor torque inthe lifting motor, and with some resistance in the rotor circuitandmotor torque in lowering at station 2.

At station I, the low voltage coil 9 of the transformer G is connectedthrough conductors m, m and m to the rotor M of motor M. The resistorsare then all out of the circuits of the rotor M Coil g is connected torotor M through conductors m, 63, 69; W, 60; and m 84, respectively. Thestator of motor C is connected to the high voltage coil 9 of the transformer. At lowering station I, the stator M is connected to the line atm directlyconnected to pole i by conductor f finger 24, contacts 24*, 23finger 23 and conductor c. M is connected to pole f bycon- The stator istact 35 pole and conductor direct to the terminal m pole f conductor a,finger 21, contacts 21*, 28, finger 28, one pole of limit-switch H,conductor 0 to terminal m pole l conductor I,

finger 24, contacts 24*, 25, finger 25, the other pole of limit-switchH, conductor 0 to terminal W. This will cause the stator M to drive therotor M At this station the following circuit torque for the regulationof he speed of motor M so that motor C will regulate the release of Ithe brake and so that the load will be lowered at a very slow speedwhich is accurately controllable and substantially independent of theweight of the load. This brake-regulation is important for closemanipulation of loads such as is necessary in assembly work or inaccurately positioning the load with respect to other elements. Atstation I there is no resistance in the circuit of rotorM. Therefore thetorque of motor M is almost zero and the regulatingbrake has todissipate the energy of the lowering load to minimize wear on thebrake-shoes.

When the drum 0 is turned to lowering station 2, the brake-regulation isretained, switches 11', d and at will remain closed, but the lowering ofthe load will be at a slightly higher speed. Fingers 46, 41, 26, 21, 23,24 will then engage contacts 46', 41', 26 21 23 24', respectively, andthe following circuit will be established to for rotor M will beestablished to energize magnet D to connect the stator of motor C to therotor M viz: pole f conductor 1 pole e of switch E, conductor 9 finger31, contacts 31, 36, 35, finger 35, conductor 9 switch (1, conductor gmagnet D conductors 9 g and 0*,

one pole of switch H, finger 25, contacts 25, 24*, finger 24, conductor1, pole f Switches (1 d (1 will then be closed to connect the stator ofmotor C through the transformer G and coninclude some resistance in thecircuit of rotor slightly greaterspeed than at station I. The

speed increase at this station is dependent on the value of theresistance then included which is selected for the increase desired.

When the drum is rotated to station}, the circuit through magnet D willbe interrupted at finger 35 and contact 35 so that said magnet will bedeenergized to open switches d d (1 and close swit'ch (2, when finger 35leaves con- A circuit from finger 31 through contacts 31 36 finger 36,conductors g switch d, magnet D conductors g g finger 23, contacts 23,24 finger 24 and conductors 1 I will onergize magnet D-, close switches11", d and d and open switch d and connect the stator C of motor C tostator M for releasing the brake by oversynchronous lowering. All threeof the resistors R R ,-R are then included in the circuits of rotor Mthe same as theyar'e at stations i, 2 and 3 during oversynchronouslowering with switch E in full line position hereinbefore described. Atthis station the lowering will be efiected at the highest speed desiredBetween stations 3 and 1 the control of thelowering of the load will bethe same as in oversynchronous lowering at said stations, alreadydescribed.

Liftino.-Lifting of the load may be selectively effected with or withoutbrake-regulation at the initial lifting station, by means of switch E.

When it is desired to regulate the application of the-brake in liftingloads, switch E is positioned as indicated by dotted lines in Fig. l.Atlifting station I, the stator M of the lifting motor M will beconnected to the line as follows:

ductors m, m and m .t0 the rotor M The operation of the impeller pump Pwill then be controlled responsively to the frequency and voltage in thecircuits of rotor M to regulate the releasing of the brake. Resistors R.and R will then be included in the following circuit of rotor M viz:terminal m conductor 69, resistor R conductor 62, finger 46, contacts46, 41 finger 41, conductor 6|, resistor R and conductor 60 to terminalm The circuit through resistor R will be open at pole e of switch E. Theresistance at station I is dimensioned so that light loads will startslowly under brake-regulation. At lifting station 2, the circuit throughmagnet D will be opened at finger 35 and contact 35 and the followingcircuit will be established for energizing magnet D viz: conductor polee of switch E, conductor 9 finger 31, contacts 31 36 finger 36,conductor 9 switch d, magnet D conductors g, g and c one pole of switchH, finger 25, contacts 25, 24 finger 24, conductor 1 pole I. At station2, the resistors R, R remain in the rotor circuit but the brake isreleased. At station 3, the resistors R and R remain included in thecircuit for rotor M and resistor R is also included and the brake isreleased. Resistor R is then included in the following circuit: terminalm conductor 64, resistor R conductor 63, finger 48, contacts 48, 41,finger 41, conductor 6|, resistor R. and conductor 60 to terminal in. Atstation 4, a portion of resistor R is short-circuited across conductor66, finger 49, contacts 49, 41 and conductor 6|. At lifting station 5, aportion of resistor R will be additionally short-circuited across finger50, contacts 50, 49, finger 49. At lowering station 6, a part ofresistor R is short-circuited across conductor 63 finger 5|, contacts5|, 5|), finger 50, resistor R At lowering station 1, all of theresistors will be short-circuited. As the resistors are progressivelyshort-circuited, the lifting speed will be gradually increased.

When lifting is to be done without brake-regulation, the switch E willbe positioned as shown in full lines in Pig. 1. At lifting station I, acircuit will be established through conductor i pole e of switch E,conductors g, 9 switch d, magnet D conductors g", g and 0 one pole ofswitch H, finger 25, contacts 25', 24', finger 24, conductor 1, pole ito close switches d", d, d. The resistors R and R will then be includedin the circuits for rotor M and the stator of motor C will be connectedto the stator M The motor C will release the brake. From loweringstations I to 1 inclusive the resistors are progressivelyshort-circuited as before described with regumagnet- 8 5.

lated brake starting and the lifting speed is gradually increased.

For some work it is desired to normally maintain brake-regulation and tooccasionally dispense with it. Fig. 5 illustrates a modification inwhich the control mechanism normally effects brake-regulation andincludes a pedal or pushbutton for temporarily eliminatingbrake-regulation when desired. In this modification the controllingmechanism includes all of the elements illustrated in Fig. i, such asthe drumcontroller and relay D but, in lieu of a switch E, devices areprovided for normally maintaining brake-regulation at all times exceptwhen the operator holds a switch closed by a pedal or push-button 84.This mechanism comprises a switch 80 operable by an electromagnet 8| andprovided with contacts for controlling lines to fingers 36 and 37 whichcontrol the circuits for operating magnetslD 13, before described. Thismechanism also includes a switch- 82 which is operable by magnet 83 andis connected to the circuits for resistors R R, R as illustrated.Switch-button or pedal 8% is held normally open by a spring 85 andcontrols switch 80 through Resistors R R, R are connected to the rotor Mand contactor-iingers, as illustrated, and are adapted to beprogressively shortcircuited, in the same manner as before described, bythe controller A during the lifting or lowering of loads. pedal 84 is inits open position, the circuit for operating magnet D to connect thestator of motor to the circuits of rotor M will be maintained closed forbrake-regulation in lowering and lifting the loads, as before described.Said circuit will :beas follows: pole j of switch F, conductors f 1switch 86, conductor g finger 31, contacts 3?, 35, conductor g switch dconductor g", magnet D conductors g g finger 23, conductor one pole ofswitch H, finger 25,

contacts M finger M, conductor 1, pole 1 In lowering, at stations I and2 or lifting, at

When the push-button or I the contacts for lifting and, as a result,brakestation i, the brake will be regulated as before described, and atsubsequent stations the resistors will be controlled by drum a, asbefore described. r

When brake-regulation is not momentarily desired, the operator willdepress the push-button or pedal 84, which will interrupt the lastdescribed circuit at switch by the following circuit, viz: pole f,conductors f f magnet 8|, conductor ,1, push-button or pedal, conductorf" and pole P. The circuit for the operation of magnet D will then beinterrupted at switch 80 and a circuit will be established fromconductor f through switch 80 and its upper contacts and conductor 9 foroperating magnet N, as hereinbefore described, to close switches d", d,d for connecting the stator of motor C to the statorM Simultaneously,current will pass from conductor 1 through magnet 83 to conductor 1 andenergize said magnet. This will close switch 82 and close the circuitsof the rotor M and connect the resistors R R, R in the rotor circuit forcontrolling the lifting mechanism, as hereinbefore described, in liftingand lowering.

When, during lifting, the load reaches its high limit, switch H may beopened by any suitable means, as well understood in the art, tointerruptthe current from the line to the stator M regulation may be maintainedduring a. plurality of stations in lowering and a single station inlifting loads.

Another characteristic is that in regulated lowering no resistance isincluded at station I and some resistance will be included at station 2,while the brake-motor C is connected to the circuits of rotor M.

The invention is not to be understood as restricted to the details setforth, since these may be modified within the scope of the appendedclaims, without departing from the spirit and scope of the invention.

Having thus described the invention, what I ent is:

1. In a control system for hoisting mechanism,

the combination of a power-supply line, an electric induction hoistingmotor comprising a stator and a rotor subject to an overhauling load, abrake normally applied to the hoisting motor, an electric motor forreleasing'the'brake, hydraulic brake-releasing means responsive to thespeed of the brake-releasing motor for regulating the release of thebrake, resistors for varying the speed of the hoisting motor, acontroller comprising switches at a series of stations for establishingcircuits for controlling the operation and speed of the hoisting motor,means responsive to the controller at one lowering station forconnecting the stator of the hoisting motor to the power-supply line,means responsive to the controller at the same station for operating thehoisting motor as a frequency and voltage converter when its rotor isdriven by an overhauling load, and electromagnetic switch meansresponsive to the controller at the same station for connecting thebrake-motor to the rotor of the hoisting-motor for the operation of thebrakeand voltage produced by the overhauling load,

for regulating the release of the brake.

2. In a control system for hoisting mechanism, the combination of apower-supply line, an electric induction hoisting motor comprising astator and a rotor subject to an overhauling load, a brake normallyapplied to the hoisting-motor, an electric motor for releasing thebrake, hydraulic brake-releasing means responsive to the speed of thebrake-releasing motor for regulating the release of the brake, resistorsfor varying the speed of the hoisting-motor, a controller comprisingswitches at a series of stations for establishing circuits forcontrolling the operation and speed of the hoisting'motor, meansresponsive to the controller at one lowering station for connecting thestator of the hoisting-motor to the power-supply line, means responsiveto the controller at the same station for operating the hoisting-motoras a frequency and voltage converter when its rotor is driven by anoverhauling load, electromagnetic switch means responsive to thecontroller at the same station for connecting .the brake-motor to therotor of the hoisting motor for the operation of the brake-motor at aspeed responsive to the frequency and voltage produced by theoverhauling load for regulating the release of the brake, and meansresponsive to the controller at the same station for selectivelyestablishing circuits for operating the hoisting-motor as anasynchronous generator and connecting the brake-motor to the stator ofthe hoisting motor for over-synchronous lowering of loads.

3. In a control system for hoisting mechanism, the combination of apower-supply line, an electric induction hoisting-motor comprising astator and a rotor subject to an overhauling load, a brake normallyapplied to the hoisting-motor, an electric motor for releasing thebrake, hydraulic brake-releasing means responsive to the speed of thebrake-releasing motor for regulating the release of the brake, resistorsfor varying the speed of the hoisting-motor, a controller comprisingswitches at a series of stations for establishing circuits forcontrolling the operation and speed of the hoisting-motor, meansresponsive to the controller at one lowering station for connecting thestator of the hoisting-motor to the powersupply line, means responsiveto the controller at the same station for operating the hoistingmotor asa frequency and voltage converter when its rotor is driven by anoverhauling load, electromagnetic switch means responsive to thecontroller at the same station for connecting the brake-motor to therotor of the hoisting-motor for the operation of the brake-motor at aspeed responsive to the frequency and voltage produced by theoverhauling load for regulating the release of the brake, and means forincluding re-- sistance in the circuit of said rotor responsively to thecontroller at the second lowering station for increasing the speed ofthe brake-motor for an increase of the lowering speed of the overhaulingload.

4. In a control system for hoisting mechanism, the combination of apower-supply line, an electric induction hoisting motor comprising astator and a rotor subject to an overhauling load, a brake normallyapplied to the hoisting motor, an electric motor for releasing thebrake, hydraulic brake-releasing means responsive to the speed of thebrake-releasing motor for regulating the release of the brake, resistorsfor varying the speed of the hoisting-motor, a controller comprisingswitches at a series of stations for establishing circuits forcontrolling the operation and speed of the hoisting-motor, meansresponsive to the controller at one lowering station for connecting thestator of the hoisting motor to the power-supply line, means responsiveto the controller at the same station for operating the hoisting-motoras a frequency and voltage converter when its rotor is driven by anoverhauling load, electromagnetic switch means responsive to thecontroller at the same station for connecting the brake-motor to therotor of the hoistingmotor for the operation of the brake-motor at aspeed responsive to the frequency and voltage produced by theoverhauling load for regulating the release of the brake, means forincluding resistance in the circuit of said rotor responsively to thecontroHeI at the second lowering station for increasing the speed of thebrake-motor for an increase of the lowering speed of the overhaulingload, and means responsive to the controller at the third loweringstation for including additional resistance in the circuit of said rotorand establishing circuits for operating the hoisting-motor as anasynchronous generator and operating the brake-motor to release thebrake for over-synchronous lowering of the loads,

5. In a control system for hoisting-mechanism, the combination of apower-supply line, an electric induction hoistingmotor comprising astator and a rotor subject to an overhauling load, a brake normallyapplied to the hoisting-motor, an electric motor for releasing thebrake, hydraulic brake-releasing means responsive to the speed of thebrake-releasing motor for regulating the release of the brake, resistorsfor varying the speed of the hoisting-motor, a controller comprisingswitches at a series of stations for establishing circuits forcontrolling the operation and speed of the hoisting-motor, meansresponsive to the controller at the first lifting station for connectingthe stator of the hoisting-motor to the power-supply line for theoperation of the rotor, electromagnetic means responsive to thecontroller at the same station for connecting the rotor to thebrake-releasing motor for the operation of the brake-motor responsivelyto the frequency and voltage in the rotor circuit, and electromagneticswitch-means responsive to the controller at the second lifting stationfor connecting the brake-motor to the stator of the hoisting motor forthe release of the brake.

6. In a control system for hoisting mechanism, the combination of apower-supply line, an electric induction hoisting-motor comprising astator and a rotor subject to an overhauling load, a brake normallyapplied to the hoisting-motor, an electric motor for releasing thebrake, hydraulic brake-releasing means responsive to the speed of thebrake-releasing motor for regulating the release of the brake, resistorsfor varying the speed of the hoisting motor, a controller comprisingswitches at a series of stations for establishing circuits forcontrolling the operation and speed of the hoisting-motor, meansresponsive to the controller at the first lifting station for connectingthe stator of the hoisting-motor to the power supply-line for theoperation of the rotor, electromagnetic means responsive to thecontroller at the same station for connecting the rotor to thebrake-releasing motor responsively to the frequency and voltage in therotor circuit, electromagnetic switch-means responsive to the controllerat the second lifting station for connecting the brake-releasing motorto the stator of the hoisting-motor for the release of the brake, andmeans for selectively establishing circuits for operating thehoisting-motor as an asynchronous generator and connecting thebrake-motor to the stator of the hoisting motor for over-synchronouslowering of loads, when the controller is at the first lifting station.

7. In a control system for hoisting mechanism, the combination of apower-supply line, an electric induction hoisting motor comprising astator and a rotor subject to an overhauling load, a brake normallyapplied to the hoisting-motor, an electric motor for releasing thebrake, hydraulic mechanism responsive to the speed of thebrake-releasing motor for regulating the release of the brake, resistorsfor varying the speed of the hoisting motor, a controller comprisingswitches at a series of lowering and lifting stations for establishingcircuits for controlling the operation and speed of the hoistingmotor,means responsive to the controller at the first lowering station forconnecting the stator of the hoisting-motor to the power-supply line,means responsive to the controller at the first lowering station foroperating the hoisting-motor as a frequency and voltage converter whenits rotor is driven by an overhauling load, electromagnetic switch-meansresponsive to the controller at the first lowering station forconnecting the brake-motor to the rotor of the hoisting-motor for theoperation of the brakemotor at a speed responsive to the frequency andvoltage produced by the overhauling load for regulating the release ofthe brake, means responsive to the controller at the first liftingstation for connecting the stator of the hoistingmotor to thepower-supply line for the operation of the rotor, electromagnetic meansresponsive to the controller at the same station for connecting therotor to the brake-releasing means for the operation of the brake-motorresponsively to the frequency and voltage in the rotor circuit, andmeans for selectively establishing circuits for operating thehoisting-motor as an asynchronous generator and connecting thebrake-motor to the stator of the hoisting-motor for over-synchronouslowering of loads when the controller is at the first lifting and thefirst lowering station.

8. In a control system for hoisting mechanism, the combination -oi apower-supply line, an electric induction hoisting motor comprising astator and a rotor subject to an overhauling load, a brake normallyapplied to the hoisting-motor, an electric motor for releasing thebrake, hydraulic mechanism responsive to the speed of thebrake-releasing motor for regulating the release of the brake, resistorsfor varyingthe speed of the hoisting-motor, a controller comprisingswitches at a series of lowering and lifting stations for establishingcircuits for controlling the operation and speed of the hoisting motor,means responsive to the controller at the first lowering station forconnecting the stator of the hoisting-motor to the power-supply line,means responsive to the controller at the first lowering station foroperating the hoistingmotor as a frequency and voltage converter whenits rotor is driven by an overhauling load, electromagnetic switch-meansresponsive to the controller at the first lowering station for conmeeting the brake-motor to the rotor of the hoisting-motor for theoperation of the brakemotor at a speed responsive to the frequency andvoltage produced by the overhauling load for regulating the release ofthe brake, means responsive to the controller at the first liftingstationfor connecting the stator of the hoistlug-motor to thepower-supply line for the operation of the rotor, and electromagneticmeans responsive to the controller at the first lifting station forconnecting the rotor to the brakereleasing means for the operation ofthe brakemotor responsively to the frequency and voltage in the rotorcircuit.

9. In a. control system for hoisting-mechanism, the combination of apower-supply line,

an electric induction hoisting-motor comprising a stator and a rotorsubject to an overhauling load, a brake normally applied to the hoistingmotor, an electric motor for releasing the brake, hydraulic mechanismresponsive to the speed of the hrake-releasing motor for readlating therelease of the brake, resistors for varying the speed of thehoisting-motor, a-controller comprising switches at a series of loweringand lifting stations for establishing circuits for controlling theoperation and speed of the hoisting-motor, means responsive to thecontroller at the first lowering station for connect ing the stator ofthe hoisting-motor to the powerupply line, means responsive to the controller at the first lowering station for operating the hoistingmotor asa frequency and voltage converter when its rotor is driven by anoverhauling load, electromagnetic switch means responsive to thecontroller at the first lowering station for connecting the brake-motorto the rotor of the hoisting-motor for the operation of the brake-motorat a speed responsive to the frequency and voltage produced by theoverhauling load for regulating the release of the brake. means forincluding resistance in the circuit of said rotor responsively to thecontroller at the second lowering station for increasing the speed ofthe brake-motor for an increase of the lowering speed of the overhaulingload, means responsive to the controller at the third lowering stationfor including additional resistance in the circuit of said rotor andestablishing circults for operating the hoisting-motor as anasynchronous generator, and operating the brake-motor to release thebrake for over-syn.- chronous lowering of the loads, means responsive tothe controller at the-first lifting station for connecting the stator ofthe hoisting-motor to the power-supply line for the operation of therotor, electromagnetic means responsive to the controller at the samestation for connecting the rotor to the brake-releasing means for theoperation of the brake-motor rcsponsively to the frequency and voltagein the rotor circuit, and electromagnetic switch-means responsive to thecontroller at the second lifting station for connecting the brake-motorto the stator of I the hoisting-motor for the release of the brake.

10. In a control system for hoisting mechanism, the combination of apower-supply line, an electric induction hoisting-motor comprising astatorand a rotor subject to an overhauling load, a brake normallyapplied to the hoistingmotor, an electric motor for releasing the brake,hydraulic mechanism responsive to the speed of the brake-releasing motorfor regulating the release of the brake, resistors for varying the speedof 'the hoisting-motor, a controller com.- prising switches at a seriesof lowering and lifting stations for establishing circuits forcontrolling the operation and speed of the hoistingrnotor, meansresponsive to the controller at the first lowering station forconnecting the stator of the hoisting-motor to the power-supply line,means responsive to the controller at the first lowering station foroperating the hoistingmotor as a frequency and voltage converter whenits rotor is driven by an overhauling load, electromagnetic switch-meansresponsive to the controller at the first lowering station forconnecting the brake-motor to the rotor of the hoisting-motor for theoperationcf the brakemotor at a speed responsive to the frequency andvoltage produced by the overhauling load for regulating the release ofthe brake, means for includ ng resistance in the circuit of said rotorresponsively to the controller at the sec-=- ond lowering station forincreasing the speed of the brake-motor for an increase of the loweringspeed of the overhauling load, means responsive to the controller at thethird lowering station for including additional resistance in thecircuit of said rotor and establishing circuits for operating thehoisting-motor as an asynchronous generator, and operating the'brakeunotor to release the brake rm: over-synchronous lowering of theloads, means respon= sive to the controller at the first lifting stationfor connecting the stator of the hcistingunotor to the power-supply linefor the operation of the rotor, electromagnetic means responsive to thecontroller at the same station for corn necting the rotor to thebrake-regulating means for the operation of the brake-motor responsivelyto the frequency and voltage in the rotor circuit, electromagneticswitch-means responas an asynchronous generator and connecting sive tothe controller at the second lifting sta- U the brake-motor to thestator 01 the hoistingtion for connecting the brake-motor to the -motorfor over-synchronous lowering of loads stator of the hoisting-motor forthe release of when the controller is at the first lifting and the thebrake, and means for selectively establish- 5 first lowering station.

ing circuits for operating the hoisting-motor ERNST L. SCHWARZ.

